This invention relates to fixing pulley wheels to plate-like structures.
There are numerous applications of pulley wheels in a wide variety of mechanical constructions. Very often the pulley wheel is to be attached to a metal sheet and it is well-known to do that by attaching a stub shaft or axle to the sheet, e.g. by spot welding and then fixing a pulley wheel thereon, the pulley wheel being retained, e.g. by a spring clip engaging in a peripheral groove in the stub shaft, conventionally with the interposition of a washer or bush. In many cases, the metal sheet then is has to be fixed in place in the device in question, for which purpose further and separate fixing means are provided. Thus the installation of a pulley wheel in a piece of equipment requires two sorts of fixing process, which is clearly consumptive of machinery, time and manual (or robotic) manipulation.
We have now found that by careful design it is possible to produce a pulley wheel arrangement, where the fixture of the stub shaft for the wheel itself and the provision of fixing means for the assembly of stub shaft on a plate-like metal substrate are combined.
GB 318 182A describes improvements in and relating to securing parts and articles to metal and other plates, sheets and the like by riveting. It discloses, in FIGS. 8 and 9 attaching a bolt with an annular shoulder to a metal plate. DE 41 31 098A discloses, in FIG. 2, a pulley mounted on a bolt.
According to a first feature of the present invention, there is provided a stud having a cylindrical shank of a first diameter connected to a shank portion of a second, smaller diameter via a shoulder having an annular groove, the shank portion mounting a shaft provided with a fixing configuration;
characterised in that
the shank is adapted to act as a stub shaft for a pulley and is provided with a head of enlarged diameter relative to the shank to retain the pulley; the end of the shank remote from the head being connected to the smaller shank portion; the annular groove extending from the plane of the shoulder towards the head; and the shaft extending away from the head.
Such a stub may be used, as set out in claim 6, to mount a pulley to a metal plate by providing in the metal plate a hole of diameter equal to or slightly exceeding that of the smaller shank portion;
placing the pulley over the first diameter shank portion, the axial dimension of the pulley being at most equal to the axial extent of the first diameter shank portion;
inserting the smaller shank portion through the hole in the metal plate, and;
cold forming the smaller diameter shank portion to expand it and fit it securely into the metal plate.
This leaves a stud attached to the metal plate with the pulley wheel mounted to one side of the plate and the shaft extending on the other side. The shaft may be fixed in place where desired simply by inserting it through a suitable hole in the structure of the machine or the like and attaching a mating fixture, for example a nut, optionally with a locking washer, if the nut is not itself self-locking, onto the shaft if it is threaded.
According to a second feature of the invention, there is provided an assembly of a stud, pulley and metal plate, wherein the stud has a head of large diameter relative to a shank extending from the head, the shank being cylindrical and having a first portion constituting a stub shaft for the pulley, and wherein the end of the shank first portion remote from the head is connected to a smaller diameter shank portion via a shoulder, and wherein located on the side of the smaller diameter shank portion and extending away from the head is a shaft having a fixing configuration, there being on one of the shoulder or the smaller diameter shank portion a torsional resistance-enhancing configuration, and wherein the metal plate has an aperture, the edges of which are at least partly deformed into contact with the torsional resistance-enhancing configuration, and the pulley being held captive between the plate and the head of the stud.
Preferably the exterior surface of the smaller diameter shank portion and/or the interior of the annular groove and/or of the shoulder if without a groove is/are provided with a torsional resistance-enhancing configuration; this may be, for example, axial ribs or radial ribs or studs or flat facets around which the metal of the plate deforms during cold-forming. Such formations render the stub shaft resistant to rotation about its axis once it is mounted to the plate, by providing a secure physical interlocking between the formations and the parts of the plate deformed against them.
If the axial dimension of the pulley wheel is less than that of the larger diameter portion of the shank, one or more spacers or washers may be provided as appropriate to prevent the pulley moving axially on the shank after the stud has been installed in the metal plate.
The present invention is of particular value in connection with the construction of automobile window movement systems, where movement of the window, e.g. up or down in a driver or passenger door, is conventionally achieved by mounting the window in generally vertically extending tracks and providing, on the bottom of the window, some form of mechanical linkage which raises or lowers the window itself. The drive for that mechanical linkage is conventionally provided either by a rotatably mounted crank handle set on the inside of a door or it may be produced from an electric motor. In either case, the conventional drive transmission method used is that of an extending belt or wire which runs over a series of pulleys. Mounting the pulleys to the usually metal plate components of the mechanism can save substantial quantities of time in the overall assembly of the window and winder gear.